The term “steganography” generally infers data hiding. One form of data hiding includes digital watermarking. Digital watermarking is a process for modifying media content to embedded a machine-readable (or machine-detectable) signal or code into the media content. For the purposes of this application, the data may be modified such that the embedded code or signal is imperceptible or nearly imperceptible to a user, yet may be detected through an automated detection process. Most commonly, digital watermarking is applied to media content such as images, audio signals, and video signals.
Digital watermarking systems may include two primary components: an embedding component that embeds a watermark in media content, and a reading component that detects and reads an embedded watermark. The embedding component (or “embedder” or “encoder”) may embed a watermark by altering data samples representing the media content in the spatial, temporal or some other domain (e.g., Fourier, Discrete Cosine or Wavelet transform domains). The reading component (or “reader” or “decoder”) analyzes target content to detect whether a watermark is present. In applications where the watermark encodes information (e.g., a message or payload), the reader may extract this information from a detected watermark.
A watermark embedding process may convert a message, signal or payload into a watermark signal. The embedding process may then combines the watermark signal with media content and possibly another signals (e.g., an orientation pattern or synchronization signal) to create watermarked media content. The process of combining the watermark signal with the media content may be a linear or non-linear function. The watermark signal may be applied by modulating or altering signal samples in a spatial, temporal or some other transform domain.
A watermark encoder may analyze and selectively adjust media content to give it attributes that correspond to the desired message symbol or symbols to be encoded. There are many signal attributes that may encode a message symbol, such as a positive or negative polarity of signal samples or a set of samples, a given parity (odd or even), a given difference value or polarity of the difference between signal samples (e.g., a difference between selected spatial intensity values or transform coefficients), a given distance value between watermarks, a given phase or phase offset between different watermark components, a modulation of the phase of the host signal, a modulation of frequency coefficients of the host signal, a given frequency pattern, a given quantizer (e.g., in Quantization Index Modulation) etc.
The present assignee's work in steganography, data hiding, digital watermarking and signal detection is reflected, e.g., in U.S. Pat. Nos. 7,072,487; 6,947,571; 6,912,295; 6,891,959; 6,763,123; 6,718,046; 6,614,914; 6,590,996; 6,522,769; 6,408,082; 6,122,403 and 5,862,260, and in published specifications WO 9953428 and WO 0007356 (corresponding to U.S. Pat. Nos. 6,449,377 and 6,345,104), and in published U.S. Patent Application No. US 2008-0298632 A1. Each of the patent documents mentioned in this paragraph is hereby incorporated by reference in its entirety. Of course, a great many other approaches are familiar to those skilled in the art. The artisan is presumed to be familiar with a full range of literature concerning steganography, data hiding and digital watermarking.
A so-called “fingerprint” may include characteristic features used to identify a video or image. Such characteristic features can be derived, calculated or extracted from an image or video itself. Some such characteristic features may include, e.g., frequency domain features, peaks, power characterizations, amplitude values, statistical features, key frame analysis, color, motion changes during a video sequence, and/or others. Characteristic features (e.g., one or more fingerprints) of artwork, or a portion thereof, can be distilled into a set of numbers, or features, which can be stored in a database, and later matched against unknown works to identify the same. A fingerprint also can be used to link to or access remote data. Example image and video fingerprinting techniques are detailed, e.g., in patent publications U.S. Pat. Nos. 7,930,546, 7,289,643, and 7,020,304 (Digimarc); U.S. Pat. No. 7,486,827 (Seiko-Epson); 20070253594 (Vobile); 20080317278 (Thomson); and 20020044659 (NEC). Each of the above patent documents is hereby incorporated by reference in its entirety.
One possible combination of the present disclosure includes a method comprising: identifying a shadow cast by a camera on a subject being imaged; and using a programmed electronic processor, redressing the shadow in connection with: i) reading a digital watermark from imagery captured of the subject, or ii) calculating a fingerprint from the imagery captured of the subject.
Another combination includes a cell phone comprising: a camera for capturing imagery; memory for buffering captured imagery; and an electronic processor programmed for: identifying a shadow cast by the cell phone on a subject being imaged by said camera; and redressing the shadow in connection with: i) reading a digital watermark from imagery captured of the subject, or ii) calculating a fingerprint from the imagery captured of the subject.
Yet another combination includes a method comprising: identifying a shadow cast by a cell phone on a subject being imaged by a camera included in the cell phone; and using a programmed electronic processor, determining a proximity of the camera to the subject based on an analysis of the shadow.
Further combinations, aspects, features and advantages will become even more apparent with reference to the following detailed description and accompanying drawing.